The present application relates to managing temperatures in hybrid power systems, and more particularly but not exclusively relates to managing temperatures for hybrid power systems having variable temperature requirements for a number of devices. Hybrid power systems include multiple power devices, for example an internal combustion engine and a battery pack. The multiple power devices have variable duty cycles and warm-up times, as well as variable optimal temperatures and variable compatible temperature ranges. Presently available have a number of drawbacks. Devices that utilize the same cooling fluid for an engine and electrical components are capable of only sub-optimal temperature control for some devices, are subject to restrictions in component order within the cooling system, and are not robust to fluctuations in the temperature of the cooling fluid. Systems that can only provide auxiliary cooling for devices cannot promote quick warm-up or holding temperatures for devices within a relatively narrow operating temperature band. Accordingly, there is a demand for further improvements in this area of technology.